The present invention relates generally to circuit boards for electronic devices and, in particular, to a circuit board with flexibility for electronic devices having a structure capable of giving connections with high reliability.
In recent years, various kinds of circuit boards with flexibility for electronic devices have been developed by providing a printed circuit on the surface of a sheet-like electrically insulating material such as polyimide resin, polyester resin and the like. Such types of circuit boards are widely employed in assembling various kinds of precision electronic devices. When these circuit boards are employed is assembling a precision electronic device, the electric connection between the terminal contact points of the circuit board, arranged in an area usually at the peripheries of the board, and other parts of the device is made in several different ways such as soldering, fastening with bolts and nuts or clamping with a specifically designed jig such as a clip (see, for example, U.S. Pat. No. 3,924,915 and Brit. Pat. No. 940,518).
Among these known methods for connecting the terminal contact points and the other parts of the device, the methods with bolts and nuts or with a clip are superior to the method employing soldering in working efficiency, but these methods comprise certain problems in obtaining sufficient reliability in the connection because of the difficulty in applying uniform contacting pressure throughout all of the contact points. Therefore, it is the usual practice in the prior art that an excessively strong pressure is applied to the connection area of the terminal contact points in order to improve the reliability in electric connection or that a cushioning material is inserted between the connection area and the means for clamping or press-contacting so that the contacting pressure is uniformly distributed over the connection area. These methods are still disadvantageous because of the insufficient reliability in connection as well as the necessity of jigs to fix the cushioning material in the predetermined positions.